Currently, watermarked paper is widely used in all fields from applications to general letters to securities with a monetary value such as share certificates, bond certificates and gift certificates, and banknotes. Among them, securities generally use paper in which, so that forgery or altering is not easily performed, a watermark is applied to the paper itself, or special printing such as micro characters, intaglio, hidden characters and fluorescent printing are applied, or a foil having a metallic luster such as a gold foil or a silver foil or a foil having a diffraction structure such as a hologram or a diffraction grating that could represent a stereoscopic image or a special decorative image by the use of light interference is applied by transferring or applying a seal (for example, see PTLs 1 and 2).
As methods and configurations for applying a watermark, there have been proposed methods such as a white watermarking method and a dark watermarking method for forming a pattern by changing a thickness of paper using a special papermaking machine, a configuration in which a base material on which a watermark pattern is previously printed is created and a paper base material is bonded onto the front and back sides of the base material, and a method in which a color former is previously applied to a base material, a paper base material is bonded to the front and back sides of the base material and finally a laser is irradiated to obtain a watermark image, and the like (for example, see PTLs 3 and 4).
Meanwhile, in recent years, for decreasing an energy consumption amount, development of a dimming mirror has progressed aiming at improvement of a heat insulating property by a light-blocking effect. A dimming mirror can be realized by forming, on a glass, a dimming mirror element in which thin-film materials are combined so as to control optical characteristics arbitrarily. In the case where all of thin-film materials can be formed from solids, a dimming mirror is allowed to be formed not only on a glass but also on a plastic film that is bendable (for example, see PTL 5, NPL 1 and the like). At present, these dimming mirror elements are limited to uses as a window glass of a vehicle or of a building, an electronic display device such as a liquid crystal display and the like, and have not been applied to other uses.